Intrusion prevention appliances have been widely available in the last few years. Published U.S. Patent Application Numbers 20030004688, 20030004689, 20030009699, 20030014662, 20030204632, 20030123452, 20030123447, 20030097557, and 20030041266 disclose systems, methods and techniques that primarily focused on content, header and state anomaly based intrusion prevention. Denial of Service attack prevention systems have also been dealt in the literature. Published US Patent Application Numbers 20030076848, 20030110274 and 20030070096, and 20020083175 disclose systems that prevent denial of service attacks or spoofed DNS messages.
As one skilled in the art knows, internet attacks have been growing in complexity and have been more wide-spread due to a variety of readily available attack toolkits. Many of the recent DoS or DDoS attacks have been on the DNS servers. By overloading the DNS servers, the attackers can easily deny access to the associated web-service or other related internet services. Clearly, a new method and system is needed to protect DNS servers from getting flooded with unwanted and illegitimate requests. The present invention addresses this need.